This invention relates to an Insulated Gate Field Effect Transistor Read Only Memory (IGFET ROM) array, and more specifically to a high density V-groove Metal-Oxide-Semiconductor (VMOS) ROM array.
As the need for larger and more powerful memories continues to grow, it becomes incumbent upon the semiconductor device manufacturer to produce larger and larger memories having higher performance characteristics on a single semiconductor chip. In order to accommodate this trend it is necessary to improve both the performance and the density of memory devices. Accordingly, attempts are made to shrink device sizes, reduce spacing between devices, and to optimize device layout. Eventually, however, yield considerations forbid the further reduction in device size. One alternative has been to turn from conventional devices to new device forms such as the VMOS transistor. This device can provide improved device characteristics as well as the potential for increased density. Heretofore, however, there has not been a practical means for employing the VMOS transistor in a ROM array nor a practical means for programming that array so as to take advantage of the potential density improvement. Further, to be used to advantage, the VMOS devices must be combined with conventional IGFET devices on the same chip.
Accordingly, it is an object of this invention to provide an improved VMOS ROM array.
It is a further object of this invention to provide a high density, high performance ROM array and method for its programming.